Grain boundary strengthening in copper/niobium multilayered foils and fine-grained niobium

• Published in: Journal of materials research 2008-02, Vol.23 (2), p.376-382
• Main Authors: Lewis, A.C., Eberl, C., Hemker, K.J., Weihs, T.P.
• Format: Article
• Language: English
• Subjects: Applied and Technical Physics; Biomaterials; Grain size; Inorganic Chemistry; Materials Engineering; Materials Science; Nanotechnology; Stress–strain relationship
• ISSN: 0884-2914; 2044-5326
• DOI: 10.1557/JMR.2008.0044

Uniaxial tensile tests were performed on Cu/Nb multilayered foils to investigate yield strength and grain boundary strengthening in the layered foils at room temperature and in fine-grained Nb at 600 °C. At room temperature, yielding in Cu/Nb multilayered foils is controlled by deformation in both layers, and grain boundary strengthening is observed with a Hall–Petch slope (kRT) of 198 ± 56 MPa·μm1/2 at a strain rate of 10−4 s−1. At 600 °C, yielding in Cu/Nb multilayered foils is controlled by deformation in just the Nb layers. Hall–Petch strengthening is observed over a range of strain rates, but the Hall–Petch slope decreases from 197 ± 71 MPa·μm1/2 for a strain rate of 10−4 s−1 to only 25 ± 40 MPa·μm1/2 for a strain rate of 10−6 s−1. The significant drop in the Hall–Petch slope for Nb with decreasing strain rate indicates a change in the controlling deformation mechanism from dislocation glide to dislocation creep.